Inductively coupled plasma powder vaporization for fabricating integrated circuits

ABSTRACT

An apparatus and method for performing material deposition on semiconductor devices. The apparatus provides an enclosure for defining a chamber. The chamber includes a metallic portion such as a conductor coil powered by a voltage generator. A gas, having a suspension of particles for treating the semiconductor devices, is introduced into the chamber and the powered conductor coil converts the gas to inductively coupled plasma and vaporizes the particles. The particles can then be deposited on the semiconductor devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention is a continuation-in-part of U.S. application Ser.No. 08/996,260 filed Dec. 22, 1997 and entitled Apparatus and Method forFabricating Spherical Shaped Semiconductor Integrated Circuits, which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

The invention relates generally to semiconductor integrated circuits,and more particularly, to an apparatus and method for fabricating aspherical-shaped semiconductor integrated circuit.

Conventional integrated circuits, or "chips," are formed from a flatsurface semiconductor wafer. The semiconductor wafer is firstmanufactured in a semiconductor material manufacturing facility and isthen provided to a fabrication facility. At the latter facility, severallayers are processed onto the semiconductor wafer surface. Oncecompleted, the wafer is then cut into one or more chips and assembledinto packages. Although the processed chip includes several layersfabricated thereon, the chip still remains relatively flat.

A fabrication facility is relatively expensive due to the enormouseffort and expense required for creating flat silicon wafers and chips.For example, manufacturing the wafers requires several high-precisionsteps including creating rod-form polycrystalline semiconductormaterial; precisely cutting ingots from the semiconductor rods; cleaningand drying the cut ingots; manufacturing a large single crystal from theingots by melting them in a quartz crucible; grinding, etching, andcleaning the surface of the crystal; cutting, lapping and polishingwafers from the crystal; and heat processing the wafers. Moreover, thewafers produced by the above processes typically have many defects whichare largely attributable to the difficulty in making a single, highlypure crystal due to the above cutting, grinding and cleaning processesas well as due to the impurities, including oxygen, associated withcontainers used in forming the crystals. These defects become more andmore prevalent as the integrated circuits formed on these wafers becomesmaller.

Another major problem associated with modern fabrication facilities forflat chips is that they require extensive and expensive equipment. Forexample, dust-free clean rooms and temperature-controlled manufacturingand storage areas are necessary to prevent the wafers and chips fromdefecting and warping. Also, these types of fabrication facilitiessuffer from a relatively inefficient throughput as well as aninefficient use of the silicon. For example, facilities using in-batchmanufacturing, where the wafers are processed by lots, must maintainhuge inventories to efficiently utilize all the equipment of thefacility. Also, because the wafers are round, and the completed chipsare rectangular, the peripheral portion of each wafer cannot be used.

Still another problem associated with modern fabrication facilities isthat they do not produce chips that are ready to use. Instead, there aremany additional steps that must be completed, including cutting andseparating the chip from the wafer; assembling the chip to a lead framewhich includes wire bonding, plastic or ceramic molding and cutting andforming the leads, positioning the assembled chip onto a printed circuitboard; and mounting the assembled chip to the printed circuit board. Thecutting and assembly steps introduce many errors and defects due to theprecise requirements of such operations. In addition, the positioningand mounting steps are naturally two-dimensional in character, andtherefore do not support curved or three dimensional areas.

Therefore, due to these and various other problems, only a few companiesin the world today can successfully manufacture conventional flat chips.Furthermore, the chips must bear a high price to cover the costs ofmanufacturing, as well as the return on initial capital and investment.

In U.S. Pat. No. 5,995,776, assigned to the same assignee as the presentapplication and hereby incorporated by reference, a method and apparatusfor manufacturing spherical-shaped semiconductor integrated circuits isdisclosed. The present invention is specific to an apparatus and methodfor performing metal deposition on the circuits.

SUMMARY OF THE INVENTION

The present invention, accordingly, provides an apparatus and method forperforming material (e.g. metal) deposition on semiconductor devices. Inone embodiment, the apparatus provides an enclosure for defining achamber. The chamber includes a metallic portion such as a conductorcoil powered by a voltage generator. A gas, having a suspension ofparticles for treating the semiconductor devices, is introduced into thechamber and the powered conductor coil converts the gas to inductivelycoupled plasma and vaporizes the particles. The particles can then bedeposited on the semiconductor devices.

Several advantages result from the foregoing. For one, the semiconductordevices can be continuously introduced into the chamber to reduce oreliminate the need for a clean room environment. Also, the chamber canbe maintained at a relatively high temperature above conventionalsemiconductor material warping or melting points. Further, the method ofthe present invention can be carried out in a relatively small space andeliminates the requirements for assembly and packaging facilities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the apparatus of the presentinvention.

FIG. 2 is a graph of temperature and vapor flux vs. location fordefining a deposition area in the apparatus of FIG. 1.

FIG. 3 is an expanded, sectional view of the apparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the reference numeral 8 refers, in general, to aprocessing device including a hollow outer sphere 10 having an inletopening 10a and an outlet opening 10b located diametrically opposite theinlet opening 10a. One end of a horizontally extending inlet conduit 12registers with the inlet opening 10a of the sphere 10, and one end of agenerally U-shaped outlet conduit 14 registers with the outlet opening10b. It is understood that the conduits 12 and 14 are connected to thesphere 10 in any known manner and, alternately, can be formed integrallywith the sphere.

A hollow inner sphere 20 extends within the sphere 10 in a coaxial,slightly spaced relationship to define a substantially spherical passage21 therebetween. The inner sphere 20 has an inlet opening 20a and anoutlet opening 20b registering with a chamber 22 defined by the interiorof the sphere, with the outlet opening 20b being located diametricallyopposite the inlet opening 20a. One end of a horizontally extendinginlet conduit 24 registers with the inlet opening 20a of the innersphere 20, and is connected to the sphere 10 in any known manner. Theinlet conduit 24 extends within the inlet conduit 12 in a spacedrelation thereto to define, with the inlet conduit 12, a cylindricalinlet passage 26 that communicates with the passage 21. Although notshown in the drawings, it is understood that the conduit 24 is supportedwithin the conduit 12 in any known manner such as by struts, or thelike. A nipple 28, or the like, is connected to the distal end portionof the inlet conduit 12 to introduce a first fluid into the passage 26,and the distal end of the inlet conduit 24 is open so as to provide aninlet to receive one or more additional fluids. For example, the firstfluid introduced into the passage 26 via the nipple 28 could be acooling fluid and the fluids introduced into the inlet conduit 24 couldbe a plasma gas and a process gas which function in a manner to bedescribed.

A second inlet opening 20c and a second outlet opening 20d are formedthrough the inner sphere 20. The openings 20c and 20d are diametricallyopposed and extend in a ninety degree, angularly spaced, relation to theopenings 20a and 20b. A pair of diametrically opposed openings 10c and10d are formed through the outer sphere 10 and are aligned with theopenings 20c and 20d, respectively, of the inner sphere 20.

A vertically extending inlet conduit 30 extends through the opening 10cin the outer sphere 10 and registers with the opening 20c of the innersphere 20. A vertically extending outlet conduit 32 extends through theopening 10d in the outer sphere 10 and registers with the opening 20d inthe inner sphere 20. A conduit 34 extends within the outlet conduit 32,through the opening 10d in the outer sphere, and also registers with theopening 20d of the inner sphere 20. The diameter of the conduit 34 isless than that of the outlet conduit 32 so as to form a cylindricalpassage 36 which also registers with the opening 20d of the inner sphere20. Although not shown in the drawings, it is understood that theconduit 34 is supported within the conduit 32 in any known manner suchas by struts, or the like.

An electrical conductor 40 is coiled around the outer surface of theconduit 12 The conductor 40 is connected to a radio frequency (RF) powergenerator 42, an impedance matching network 44, and a control panel 46for creating a radio frequency signal in connection with a plasmaprocess that may be performed in connection with the chamber 22 asdescribed below. The RF generator 42, matching network 44, and controlpanel 46 are conventional devices for producing plasma torches.

In operation, a plurality of members 50, each of a semiconductormaterial, are introduced into the inlet conduit 30 and pass into thechamber 22 in the inner sphere 20. The members 50 are preferably of agenerally spherical shape and could be of the same type formed accordingto the technique disclosed in the above-identified and presentlyincorporated U.S. Pat. No. 5,995,776. After traversing the interior ofthe chamber 22, the members 50 pass through the outlet opening 20d inthe inner sphere 20 before discharging from the chamber 22 through theconduit 32. The introduction and discharge of the members 50 in thismanner is controlled to prevent the accumulation of a relatively largenumber of members in the chamber 22 at the same time. To this end, afluid, such as an inert carrier gas, is introduced into the conduit 34and therefore passes upwardly, as viewed in the drawing, into thechamber 22, with the velocity of the gas being controlled so that thedischarge of the members 50 through the conduit 32 is controlled.

During this flow of the members 50 through the chamber, one or moregases are selectively introduced into the inlet end of the inlet conduit24 and thus flow directly into the chamber 22. The particular gases thatare introduced into the chamber depends on the specific desiredtreatment of the members 50. As an example, a high-purity argon gas isintroduced into the conduit 24 and passes into and through the chamber22 in a direction that extends approximately ninety degrees to thedirection of the passage of the members 50 through the chamber. This gas(hereinafter referred to as a "plasma gas") establishes a toroidalplasma torch region 52, shown enclosed by the phantom lines in thedrawing, through which the members 50 pass. The plasma gas thereforepasses over the members 50 in the chamber and comes into intimatecontact with the members. The velocity and mass flow of the plasma gasintroduced into the chamber 22 in this manner is controlled so that theplasma gas passes through the chamber, exits the chamber through theoutlet opening 20b in the inner sphere 20, and passes into the conduit14 for discharge. The conduit 14 also asserts a negative pressure,thereby reducing the atmospheric pressure inside the chamber 22.

During the passage of the plasma gas through the chamber 22, the RF coil40 is activated and the plasma gas, in combination with RF current fromthe coil, becomes an inductively coupled plasma. As a result, relativelyhigh energy is created and applied to the region 52 in the chamber 22.Since this formation of an inductively coupled plasma, and the resultantcreation of relatively high energy is well known in the art it will notbe described in any further detail.

A suspension of fine powder particles 56 is also selectively introducedinto the inlet end of the inlet conduit 24 and thus flows directly intothe chamber 22. The plasma gas is used to suspend the particles 56 andinject the particles into a central portion of the region 52. Theparticles 56 can be metals, such as Al, Cu, W, or Ti. Alternatively, theparticles 56 may be alumina, silica, nitrides, or a mixture of materials(e.g., a mechanical alloy). As a result, the processing device 8 may bethe sole tool used to coat semiconductor spherical integrated circuits.The size of the particles 56 are in the micron to submicron range sothat they can fully melt and subsequently vaporize in the inductivelycoupled plasma. The purity of the initial powder is essential forforming the resulting thin films of extra high purity.

Alternatively, a metal organic compound (e.g., Al containing metalorganics such as trimethyl-aluminum, dimethyl-aluminum-hydride, ortri-isobutyl-aluminum) can be introduced into the plasma gas. Further, amixture of metal organics and an inert gas (e.g., Ar or N₂) can be usedto facilitate formation of inductively coupled plasma. The metalorganics are injected in a controlled portion of region 52 and theinductively coupled plasma is formed therein. As a result of the metalorganic dissolution, a thin layer of metal (e.g., Al) material is formedon the surface of the members 50. This layer can be used as a contactlayer as described below.

Referring also to FIG. 2, a central portion of the region 52(graphically represented as the area between boundaries r1 and r2 andhereinafter designated deposition area r1-r2) has less density of plasmaas opposed to the outer regions of the toroidal plasma, discussed ingreater detail below. The boundary r1 of the deposition area r1-r2 isdefined as the location in which the vapor flux of the particles 56starts solidifying, while sufficient flux of the vapor still exists. Theboundary r2 is defined as the location in which the temperature in thechamber is less than the melting point of silicon so as not to melt themembers 50.

The particles 56 injected to the plasma region become vaporized by hightemperatures existing within the region 52. The temperature range withinthe thermal atmospheric inductively coupled plasma may vary from about5,000K to above 15,000K, depending on the power and frequency suppliedby the RF generator 42. In the preferred embodiment, the RF generator 42produces a maximum RF power of 2 kW and a working frequency of 13.56MHz. It is understood, however, that other RF powers and frequencies mayalso be used.

Referring to FIG. 3, the particles 56 passing through the region 52start melting 60 and subsequently vaporize 62. The resultant vaportravels further through the region 52 into the deposition area r1-r2.The members 50 also pass through the deposition area r1-r2 for aduration long enough for depositing a thin film 70. The rate at whichthe members 50 travel can be adjusted by the flow of gas through theconduit 34, described in greater detail above. Also, the members 50 spinto facilitate uniform film coverage. One example of a thin film that canbe made by the described technique is a thin metal (e.g., Ti) contactlayer for use in a contact stack such as Ti/TiN/Al.

The apparatus and method of the present invention leads to severaladvantages. For one, the continuous flow of the members 50 through thechamber 22 reduces or eliminates the need for batch processing. Also,the chamber can be selectively maintained at a relatively hightemperature at or above the warping or melting temperature of themembers 50, by controlling the amount of inductively coupled plasma gasformed in the chambers. Further, the spherical shape of the members 50provide much greater surface area on which the process gas acts, whencompared to the surface area of a conventional flat semiconductor. Also,the method of the present invention can be carried out in a relativelysmall space and eliminates the requirements for large facilities.

It is understood that several variations may be made in the foregoing.For example, several separate inductively coupled plasma torches can beinstalled to increase the process throughput. Also the members 50 mayhave the thermal silicon oxide or other elements of an integratedcircuit already formed thereon. Other modifications, changes andsubstitutions are intended in the foregoing disclosure and in someinstances some features of the invention will be employed without acorresponding use of other features. Accordingly, it is appropriate thatthe appended claims be construed broadly and in a manner consistent withthe scope of the invention.

What is claimed is:
 1. An apparatus for performing material depositionon semiconductor devices, the apparatus comprising:an enclosure defininga chamber, the enclosure containing a plurality of apertures and ametallic portion; a voltage generator electrically connected to themetallic portion; a first inlet registering with the chamber forreceiving a plurality of semiconductor devices; a second inletregistering with the chamber for receiving at least one gas for treatingthe semiconductor devices, the gas including a suspension of particles;and a first outlet registering with the chamber for receiving anddischarging the semiconductor devices from the chamber; wherein thevoltage generator supplies a bias to the metallic portion, therebyconverting the gas to an inductively coupled plasma and vaporizing theparticles, and wherein the semiconductor devices are deposited with thevaporized particles as the semiconductor devices move from the firstinlet to the first outlet.
 2. The apparatus of claim 1 furthercomprising a second outlet registering with the chamber for receivingand discharging the gas from the chamber.
 3. The apparatus of claim 2further comprising a pressure means for altering the pressure inside thechamber.
 4. The apparatus of claim 1 wherein the inductively coupledplasma forms a plasma torch inside the chamber and the semiconductordevices pass through a predefined portion of the plasma torch.
 5. Theapparatus of claim 4 wherein the predefined area of plasma torch has atemperature below a melting point of the semiconductor material and avapor flux above a solidification point of the particles.
 6. Theapparatus of claim 2 wherein the first outlet is diametrically opposedto the first inlet and wherein the second outlet is diametricallyopposed to the second inlet.
 7. The apparatus of claim 1 furthercomprising:a third inlet registering with the chamber for receiving asecond gas for treating the semiconductor devices, the second gas alsoincluding a suspension of particles.
 8. The apparatus of claim 1 whereinthe particles are one of either aluminum, copper, tungsten, or titanium.9. The apparatus of claim 1 wherein the particles are one of eitheralumina, silica, or nitride.
 10. The apparatus of claim 1 wherein theparticles are an alloy.
 11. The apparatus of claim 1 wherein thesemiconductor devices move from the first inlet to the first outletwithout contacting each other.
 12. The apparatus of claim 1 wherein thesemiconductor devices move from the first inlet to the first outletwithout contacting the enclosure.
 13. The apparatus of claim 1 whereinthe semiconductor devices are substantially spherical in shape andwherein an entire outer surface of each semiconductor device isdeposited with the particles.